/**
 * @file
 * Incluse internet checksum functions.\n
 *
 * These are some reference implementations of the checksum algorithm, with the
 * aim of being simple, correct and fully portable. Checksumming is the
 * first thing you would want to optimize for your platform. If you create
 * your own version, link it in and in your cc.h put:
 *
 * \#define LWIP_CHKSUM your_checksum_routine
 *
 * Or you can select from the implementations below by defining
 * LWIP_CHKSUM_ALGORITHM to 1, 2 or 3.
 */

/*
 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification,
 * are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 *
 * This file is part of the lwIP TCP/IP stack.
 *
 * Author: Adam Dunkels <adam@sics.se>
 *
 */

#include "lwip/opt.h"

#include "lwip/inet_chksum.h"
#include "lwip/def.h"
#include "lwip/ip_addr.h"

#include <string.h>

#ifndef LWIP_CHKSUM
	#define LWIP_CHKSUM lwip_standard_chksum
	#ifndef LWIP_CHKSUM_ALGORITHM
		#define LWIP_CHKSUM_ALGORITHM 2
	#endif
	u16_t lwip_standard_chksum(const void* dataptr, int len);
#endif
/* If none set: */
#ifndef LWIP_CHKSUM_ALGORITHM
	#define LWIP_CHKSUM_ALGORITHM 0
#endif

#if (LWIP_CHKSUM_ALGORITHM == 1) /* Version #1 */
/**
 * lwip checksum
 *
 * @param dataptr points to start of data to be summed at any boundary
 * @param len length of data to be summed
 * @return host order (!) lwip checksum (non-inverted Internet sum)
 *
 * @note accumulator size limits summable length to 64k
 * @note host endianess is irrelevant (p3 RFC1071)
 */
u16_t
lwip_standard_chksum(const void* dataptr, int len)
{
	u32_t acc;
	u16_t src;
	const u8_t* octetptr;

	acc = 0;
	/* dataptr may be at odd or even addresses */
	octetptr = (const u8_t*)dataptr;

	while(len > 1) {
		/* declare first octet as most significant
		   thus assume network order, ignoring host order */
		src = (*octetptr) << 8;
		octetptr++;
		/* declare second octet as least significant */
		src |= (*octetptr);
		octetptr++;
		acc += src;
		len -= 2;
	}

	if(len > 0) {
		/* accumulate remaining octet */
		src = (*octetptr) << 8;
		acc += src;
	}

	/* add deferred carry bits */
	acc = (acc >> 16) + (acc & 0x0000ffffUL);

	if((acc & 0xffff0000UL) != 0) {
		acc = (acc >> 16) + (acc & 0x0000ffffUL);
	}

	/* This maybe a little confusing: reorder sum using lwip_htons()
	   instead of lwip_ntohs() since it has a little less call overhead.
	   The caller must invert bits for Internet sum ! */
	return lwip_htons((u16_t)acc);
}
#endif

#if (LWIP_CHKSUM_ALGORITHM == 2) /* Alternative version #2 */
/*
 * Curt McDowell
 * Broadcom Corp.
 * csm@broadcom.com
 *
 * IP checksum two bytes at a time with support for
 * unaligned buffer.
 * Works for len up to and including 0x20000.
 * by Curt McDowell, Broadcom Corp. 12/08/2005
 *
 * @param dataptr points to start of data to be summed at any boundary
 * @param len length of data to be summed
 * @return host order (!) lwip checksum (non-inverted Internet sum)
 */
u16_t
lwip_standard_chksum(const void* dataptr, int len)
{
	const u8_t* pb = (const u8_t*)dataptr;
	const u16_t* ps;
	u16_t t = 0;
	u32_t sum = 0;
	int odd = ((mem_ptr_t)pb & 1);

	/* Get aligned to u16_t */
	if(odd && len > 0) {
		((u8_t*)&t)[1] = *pb++;
		len--;
	}

	/* Add the bulk of the data */
	ps = (const u16_t*)(const void*)pb;

	while(len > 1) {
		sum += *ps++;
		len -= 2;
	}

	/* Consume left-over byte, if any */
	if(len > 0) {
		((u8_t*)&t)[0] = *(const u8_t*)ps;
	}

	/* Add end bytes */
	sum += t;

	/* Fold 32-bit sum to 16 bits
	   calling this twice is probably faster than if statements... */
	sum = FOLD_U32T(sum);
	sum = FOLD_U32T(sum);

	/* Swap if alignment was odd */
	if(odd) {
		sum = SWAP_BYTES_IN_WORD(sum);
	}

	return (u16_t)sum;
}
#endif

#if (LWIP_CHKSUM_ALGORITHM == 3) /* Alternative version #3 */
/**
 * An optimized checksum routine. Basically, it uses loop-unrolling on
 * the checksum loop, treating the head and tail bytes specially, whereas
 * the inner loop acts on 8 bytes at a time.
 *
 * @arg start of buffer to be checksummed. May be an odd byte address.
 * @len number of bytes in the buffer to be checksummed.
 * @return host order (!) lwip checksum (non-inverted Internet sum)
 *
 * by Curt McDowell, Broadcom Corp. December 8th, 2005
 */
u16_t
lwip_standard_chksum(const void* dataptr, int len)
{
	const u8_t* pb = (const u8_t*)dataptr;
	const u16_t* ps;
	u16_t t = 0;
	const u32_t* pl;
	u32_t sum = 0, tmp;
	/* starts at odd byte address? */
	int odd = ((mem_ptr_t)pb & 1);

	if(odd && len > 0) {
		((u8_t*)&t)[1] = *pb++;
		len--;
	}

	ps = (const u16_t*)(const void*)pb;

	if(((mem_ptr_t)ps & 3) && len > 1) {
		sum += *ps++;
		len -= 2;
	}

	pl = (const u32_t*)(const void*)ps;

	while(len > 7)  {
		tmp = sum + *pl++;          /* ping */

		if(tmp < sum) {
			tmp++;                    /* add back carry */
		}

		sum = tmp + *pl++;          /* pong */

		if(sum < tmp) {
			sum++;                    /* add back carry */
		}

		len -= 8;
	}

	/* make room in upper bits */
	sum = FOLD_U32T(sum);

	ps = (const u16_t*)pl;

	/* 16-bit aligned word remaining? */
	while(len > 1) {
		sum += *ps++;
		len -= 2;
	}

	/* dangling tail byte remaining? */
	if(len > 0) {                 /* include odd byte */
		((u8_t*)&t)[0] = *(const u8_t*)ps;
	}

	sum += t;                     /* add end bytes */

	/* Fold 32-bit sum to 16 bits
	   calling this twice is probably faster than if statements... */
	sum = FOLD_U32T(sum);
	sum = FOLD_U32T(sum);

	if(odd) {
		sum = SWAP_BYTES_IN_WORD(sum);
	}

	return (u16_t)sum;
}
#endif

/** Parts of the pseudo checksum which are common to IPv4 and IPv6 */
static u16_t
inet_cksum_pseudo_base(struct pbuf* p, u8_t proto, u16_t proto_len, u32_t acc)
{
	struct pbuf* q;
	u8_t swapped = 0;

	/* iterate through all pbuf in chain */
	for(q = p; q != NULL; q = q->next) {
		LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
		                         (void*)q, (void*)q->next));
		acc += LWIP_CHKSUM(q->payload, q->len);
		/*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
		/* just executing this next line is probably faster that the if statement needed
		   to check whether we really need to execute it, and does no harm */
		acc = FOLD_U32T(acc);

		if(q->len % 2 != 0) {
			swapped = 1 - swapped;
			acc = SWAP_BYTES_IN_WORD(acc);
		}

		/*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
	}

	if(swapped) {
		acc = SWAP_BYTES_IN_WORD(acc);
	}

	acc += (u32_t)lwip_htons((u16_t)proto);
	acc += (u32_t)lwip_htons(proto_len);

	/* Fold 32-bit sum to 16 bits
	   calling this twice is probably faster than if statements... */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);
	LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
	return (u16_t)~(acc & 0xffffUL);
}

#if LWIP_IPV4
/* inet_chksum_pseudo:
 *
 * Calculates the IPv4 pseudo Internet checksum used by TCP and UDP for a pbuf chain.
 * IP addresses are expected to be in network byte order.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param src source ip address (used for checksum of pseudo header)
 * @param dst destination ip address (used for checksum of pseudo header)
 * @param proto ip protocol (used for checksum of pseudo header)
 * @param proto_len length of the ip data part (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
inet_chksum_pseudo(struct pbuf* p, u8_t proto, u16_t proto_len,
                   const ip4_addr_t* src, const ip4_addr_t* dest)
{
	u32_t acc;
	u32_t addr;

	addr = ip4_addr_get_u32(src);
	acc = (addr & 0xffffUL);
	acc += ((addr >> 16) & 0xffffUL);
	addr = ip4_addr_get_u32(dest);
	acc += (addr & 0xffffUL);
	acc += ((addr >> 16) & 0xffffUL);
	/* fold down to 16 bits */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);

	return inet_cksum_pseudo_base(p, proto, proto_len, acc);
}
#endif /* LWIP_IPV4 */

#if LWIP_IPV6
/**
 * Calculates the checksum with IPv6 pseudo header used by TCP and UDP for a pbuf chain.
 * IPv6 addresses are expected to be in network byte order.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param proto ipv6 protocol/next header (used for checksum of pseudo header)
 * @param proto_len length of the ipv6 payload (used for checksum of pseudo header)
 * @param src source ipv6 address (used for checksum of pseudo header)
 * @param dest destination ipv6 address (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
ip6_chksum_pseudo(struct pbuf* p, u8_t proto, u16_t proto_len,
                  const ip6_addr_t* src, const ip6_addr_t* dest)
{
	u32_t acc = 0;
	u32_t addr;
	u8_t addr_part;

	for(addr_part = 0; addr_part < 4; addr_part++) {
		addr = src->addr[addr_part];
		acc += (addr & 0xffffUL);
		acc += ((addr >> 16) & 0xffffUL);
		addr = dest->addr[addr_part];
		acc += (addr & 0xffffUL);
		acc += ((addr >> 16) & 0xffffUL);
	}

	/* fold down to 16 bits */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);

	return inet_cksum_pseudo_base(p, proto, proto_len, acc);
}
#endif /* LWIP_IPV6 */

/* ip_chksum_pseudo:
 *
 * Calculates the IPv4 or IPv6 pseudo Internet checksum used by TCP and UDP for a pbuf chain.
 * IP addresses are expected to be in network byte order.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param src source ip address (used for checksum of pseudo header)
 * @param dst destination ip address (used for checksum of pseudo header)
 * @param proto ip protocol (used for checksum of pseudo header)
 * @param proto_len length of the ip data part (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
ip_chksum_pseudo(struct pbuf* p, u8_t proto, u16_t proto_len,
                 const ip_addr_t* src, const ip_addr_t* dest)
{
#if LWIP_IPV6

	if(IP_IS_V6(dest)) {
		return ip6_chksum_pseudo(p, proto, proto_len, ip_2_ip6(src), ip_2_ip6(dest));
	}

#endif /* LWIP_IPV6 */
#if LWIP_IPV4 && LWIP_IPV6
	else
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_IPV4
	{
		return inet_chksum_pseudo(p, proto, proto_len, ip_2_ip4(src), ip_2_ip4(dest));
	}

#endif /* LWIP_IPV4 */
}

/** Parts of the pseudo checksum which are common to IPv4 and IPv6 */
static u16_t
inet_cksum_pseudo_partial_base(struct pbuf* p, u8_t proto, u16_t proto_len,
                               u16_t chksum_len, u32_t acc)
{
	struct pbuf* q;
	u8_t swapped = 0;
	u16_t chklen;

	/* iterate through all pbuf in chain */
	for(q = p; (q != NULL) && (chksum_len > 0); q = q->next) {
		LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
		                         (void*)q, (void*)q->next));
		chklen = q->len;

		if(chklen > chksum_len) {
			chklen = chksum_len;
		}

		acc += LWIP_CHKSUM(q->payload, chklen);
		chksum_len -= chklen;
		LWIP_ASSERT("delete me", chksum_len < 0x7fff);
		/*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
		/* fold the upper bit down */
		acc = FOLD_U32T(acc);

		if(q->len % 2 != 0) {
			swapped = 1 - swapped;
			acc = SWAP_BYTES_IN_WORD(acc);
		}

		/*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
	}

	if(swapped) {
		acc = SWAP_BYTES_IN_WORD(acc);
	}

	acc += (u32_t)lwip_htons((u16_t)proto);
	acc += (u32_t)lwip_htons(proto_len);

	/* Fold 32-bit sum to 16 bits
	   calling this twice is probably faster than if statements... */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);
	LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
	return (u16_t)~(acc & 0xffffUL);
}

#if LWIP_IPV4
/* inet_chksum_pseudo_partial:
 *
 * Calculates the IPv4 pseudo Internet checksum used by TCP and UDP for a pbuf chain.
 * IP addresses are expected to be in network byte order.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param src source ip address (used for checksum of pseudo header)
 * @param dst destination ip address (used for checksum of pseudo header)
 * @param proto ip protocol (used for checksum of pseudo header)
 * @param proto_len length of the ip data part (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
inet_chksum_pseudo_partial(struct pbuf* p, u8_t proto, u16_t proto_len,
                           u16_t chksum_len, const ip4_addr_t* src, const ip4_addr_t* dest)
{
	u32_t acc;
	u32_t addr;

	addr = ip4_addr_get_u32(src);
	acc = (addr & 0xffffUL);
	acc += ((addr >> 16) & 0xffffUL);
	addr = ip4_addr_get_u32(dest);
	acc += (addr & 0xffffUL);
	acc += ((addr >> 16) & 0xffffUL);
	/* fold down to 16 bits */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);

	return inet_cksum_pseudo_partial_base(p, proto, proto_len, chksum_len, acc);
}
#endif /* LWIP_IPV4 */

#if LWIP_IPV6
/**
 * Calculates the checksum with IPv6 pseudo header used by TCP and UDP for a pbuf chain.
 * IPv6 addresses are expected to be in network byte order. Will only compute for a
 * portion of the payload.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param proto ipv6 protocol/next header (used for checksum of pseudo header)
 * @param proto_len length of the ipv6 payload (used for checksum of pseudo header)
 * @param chksum_len number of payload bytes used to compute chksum
 * @param src source ipv6 address (used for checksum of pseudo header)
 * @param dest destination ipv6 address (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
ip6_chksum_pseudo_partial(struct pbuf* p, u8_t proto, u16_t proto_len,
                          u16_t chksum_len, const ip6_addr_t* src, const ip6_addr_t* dest)
{
	u32_t acc = 0;
	u32_t addr;
	u8_t addr_part;

	for(addr_part = 0; addr_part < 4; addr_part++) {
		addr = src->addr[addr_part];
		acc += (addr & 0xffffUL);
		acc += ((addr >> 16) & 0xffffUL);
		addr = dest->addr[addr_part];
		acc += (addr & 0xffffUL);
		acc += ((addr >> 16) & 0xffffUL);
	}

	/* fold down to 16 bits */
	acc = FOLD_U32T(acc);
	acc = FOLD_U32T(acc);

	return inet_cksum_pseudo_partial_base(p, proto, proto_len, chksum_len, acc);
}
#endif /* LWIP_IPV6 */

/* ip_chksum_pseudo_partial:
 *
 * Calculates the IPv4 or IPv6 pseudo Internet checksum used by TCP and UDP for a pbuf chain.
 *
 * @param p chain of pbufs over that a checksum should be calculated (ip data part)
 * @param src source ip address (used for checksum of pseudo header)
 * @param dst destination ip address (used for checksum of pseudo header)
 * @param proto ip protocol (used for checksum of pseudo header)
 * @param proto_len length of the ip data part (used for checksum of pseudo header)
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
ip_chksum_pseudo_partial(struct pbuf* p, u8_t proto, u16_t proto_len,
                         u16_t chksum_len, const ip_addr_t* src, const ip_addr_t* dest)
{
#if LWIP_IPV6

	if(IP_IS_V6(dest)) {
		return ip6_chksum_pseudo_partial(p, proto, proto_len, chksum_len, ip_2_ip6(src), ip_2_ip6(dest));
	}

#endif /* LWIP_IPV6 */
#if LWIP_IPV4 && LWIP_IPV6
	else
#endif /* LWIP_IPV4 && LWIP_IPV6 */
#if LWIP_IPV4
	{
		return inet_chksum_pseudo_partial(p, proto, proto_len, chksum_len, ip_2_ip4(src), ip_2_ip4(dest));
	}

#endif /* LWIP_IPV4 */
}

/* inet_chksum:
 *
 * Calculates the Internet checksum over a portion of memory. Used primarily for IP
 * and ICMP.
 *
 * @param dataptr start of the buffer to calculate the checksum (no alignment needed)
 * @param len length of the buffer to calculate the checksum
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */

u16_t
inet_chksum(const void* dataptr, u16_t len)
{
	return (u16_t)~(unsigned int)LWIP_CHKSUM(dataptr, len);
}

/**
 * Calculate a checksum over a chain of pbufs (without pseudo-header, much like
 * inet_chksum only pbufs are used).
 *
 * @param p pbuf chain over that the checksum should be calculated
 * @return checksum (as u16_t) to be saved directly in the protocol header
 */
u16_t
inet_chksum_pbuf(struct pbuf* p)
{
	u32_t acc;
	struct pbuf* q;
	u8_t swapped;

	acc = 0;
	swapped = 0;

	for(q = p; q != NULL; q = q->next) {
		acc += LWIP_CHKSUM(q->payload, q->len);
		acc = FOLD_U32T(acc);

		if(q->len % 2 != 0) {
			swapped = 1 - swapped;
			acc = SWAP_BYTES_IN_WORD(acc);
		}
	}

	if(swapped) {
		acc = SWAP_BYTES_IN_WORD(acc);
	}

	return (u16_t)~(acc & 0xffffUL);
}

/* These are some implementations for LWIP_CHKSUM_COPY, which copies data
 * like MEMCPY but generates a checksum at the same time. Since this is a
 * performance-sensitive function, you might want to create your own version
 * in assembly targeted at your hardware by defining it in lwipopts.h:
 *   #define LWIP_CHKSUM_COPY(dst, src, len) your_chksum_copy(dst, src, len)
 */

#if (LWIP_CHKSUM_COPY_ALGORITHM == 1) /* Version #1 */
/** Safe but slow: first call MEMCPY, then call LWIP_CHKSUM.
 * For architectures with big caches, data might still be in cache when
 * generating the checksum after copying.
 */
u16_t
lwip_chksum_copy(void* dst, const void* src, u16_t len)
{
	MEMCPY(dst, src, len);
	return LWIP_CHKSUM(dst, len);
}
#endif /* (LWIP_CHKSUM_COPY_ALGORITHM == 1) */
